Nonwoven fabrics and fabric laminates from multiconstituent polyolefin fibers

ABSTRACT

Nonwoven fabrics and fabric laminates are formed from continuous filaments or staple fibers of a select blend of specific grades of polyethylene and polypropylene which give improved fabric performance not heretofore recognized or described, such as high abrasion resistance, good tensile properties, excellent softness and the like. Furthermore, these blends have excellent melt spinning and processing properties which permit efficiently producing nonwoven fabrics at high productivity levels. The polymers are present as a lower-melting dominant continuous phase and at least one higher-melting noncontinuous phase dispersed therein. The lower-melting continuous phase forms at least 70 percent by weight of the fiber and comprises a linear low density polyethylene polymer of a melt index of greater than 10 and a density of less than 0.945 g/cc. At least one higher-melting noncontinuous phase comprises a polypropylene polymer with melt flow rate of greater than 20 g/10 min.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of Ser. No. 08/815,551,filed Mar. 12, 1997, U.S. Pat. Ser. No. 6,207,602, which is acontinuation application of Ser. No. 08/648,201, filed May 14,1996, nowabandoned, which is a continuation application of Ser. No. 08/344,419,filed Nov. 23, 1994, now abandoned.

This invention relates to nonwoven fabrics and to fabric laminates whichcomprise multiconstituent fibers formed from a select combination ofpolyolefin polymers. The invention more particularly relates to nonwovenfabrics and laminates of the type described having improved fabricproperties and processing characteristics.

Nonwoven fabrics produced from spun polymer materials are used in avariety of different applications. Among other uses, such nonwovenfabrics are employed as the cover sheet for disposable diapers orsanitary products. There is considerable interest in making disposablediapers more comfortable and better fitting to the baby. An importantpart of the diaper comfort is the softness or hardness of the nonwovensused to make the diaper, including the diaper topsheet, barrier legcuffs, and in some advanced designs, the fabric laminated to thebacksheet film. In some diaper designs, a high degree of fabricelongation is needed to cooperate with elastic components for achievinga soft comfortable fit.

One approach to improved diaper topsheet softness is to use linear lowdensity polyethylene (LLDPE) as the resin instead of polypropylene forproducing spunbonded diaper nonwoven fabrics. For example, Fowells U.S.Pat. No. 4,644,045 describes spunbonded nonwoven fabrics havingexcellent softness properties produced from linear low densitypolyethylene. However, the above-described softness of LLDPE spunbondedfabric has never been widely utilized because of the difficulty inachieving acceptable abrasion resistance in such products. The bondingof LLDPE filaments into a spunbonded web with acceptable abrasionresistance has proven to be very difficult. Acceptable fiber tie down isobserved at a temperature just below the point that the filaments beginto melt and stick to the calender. This very narrow bonding window hasmade the production of LLDPE spunbond fabrics with acceptable abrasionresistance very difficult. Thus, the softness advantage offered by LLDPEspunbonded fabrics has not been successfully captured in themarketplace.

The present invention is based upon the discovery that blending arelatively small proportion of polypropylene of a select class with thepolyethylene imparts greatly increased abrasion resistance to a nonwovenfabric formed from the polymer blend, without significant adverse effecton the fabric softness properties. It is believed that the polyethyleneand the polypropylene form distinct phases in the filaments. Thelower-melting polyethylene is present as a dominant continuous phase andthe higher-melting polypropylene is dispersed in the dominantpolyethylene phase.

A number of prior publications describe fibers formed of blends oflinear low density polyethylene and polypropylene. For example, U.S.Pat. No. 4,839,228 and EP 394,954 teach that useful fibers are formedfrom blends which are predominantly polypropylene. WO 90/10672 describesthat useful fibers are prepared from blends of polypropylene andpolyethylene, especially LLDPE, where the ratio of polypropylene topolyethylene is from 0.6 to 1.5. U.S. Pat. No. 4,874,666 describesfibers formed from a blend of LLDPE and high molecular weightcrystalline polypropylene of melt flow rate below 20 g/10 minutes. U.S.Pat. Nos. 4,632,861 and 4,634,739 describe fibers formed from a blend ofa branched low density polyethylene blended with from 5 to 35 percentpolypropylene.

SUMMARY OF THE INVENTION

In accordance with the present invention, nonwoven fabrics and nonwovenfabric laminates are formed from fibers of a select blend of specificgrades of polyethylene and polypropylene which give improved fabricperformance not heretofore recognized or described, such as highabrasion resistance, good tensile properties, excellent softness and thelike. Furthermore, these blends have excellent melt spinning andprocessing properties which permit efficiently producing nonwovenfabrics at high productivity levels.

The nonwoven fabrics of the present invention are comprised of fibrousmaterial in the form of continuous filaments or staple fibers of a sizeless than 15 dtex/filament formed of a dispersed blend of at least twodifferent polyolefin polymers. The polymers are present as alower-melting dominant continuous phase and at least one higher-meltingnoncontinuous phase dispersed therein. The lower-melting continuousphase forms at least 70 percent by weight of the fiber. The physical andrheological behavior of these blends is part of a phenomenon observed byapplicants wherein a small amount of a higher modulus polymer reinforcesa softer, lower-modulus polymer and gives the blend better spinning,bonding and strength characteristics than the individual constituents.The lower melting, relatively low molulus polyethylene providesdesirable properties such as softness, elongation and drape; while thehigher-melting, higher modulus polypropylene phase imparts one or moreof the following properties to the dominant phase: improved ability tobond the web; improved filament tie-down (reduces fuzz); improved webproperties—tensiles, and/or elongation and/or toughness; rheologicalcharacteristics which improve spinning performance and/or web formation(filament distribution).

According to one advantageous and important aspect of the presentinvention, the lower-melting continuous phase comprises a linear lowdensity polyethylene polymer of a melt index of greater than 10 (ASTMD1238-89, 190° C.) and a density of less than 0.945 g/cc (ASTMD-792). Atleast one higher-melting noncontinuous phase comprises a polypropylenepolymer with melt flow rate of greater than 20 g/10 min (ASTM D1238-89,230° C.).

In one of the preferred embodiments of the invention, the lower-meltingcontinuous phase forms at least 80 percent by weight of the fiber andcomprises a linear low density polyethylene having a density of0.90-0.945 g/cc and a melt index of greater than 25 g/10 minutes.

In another preferred embodiment, said lower-melting polymer phasecomprises linear low density polyethylene as described above and saidhigher-melting polymer phase comprises an isotactic polypropylene with amelt flow rate greater than 30 g/10 minutes.

In still another preferred embodiment said lower-melting polymer phasecomprises at least 80 percent by weight low pressure, solution process,linear short chain branched polyethylene with a melt index of greaterthan 30 and a density of 0.945 g/cc and said higher-melting polymerphase comprises 1 to 20 percent by weight of isotactic polypropylene.

In another embodiment of the invention, said lower-melting polymer phasecomprises linear low density polyethylene with a melt index of 27 andsaid higher-melting polymer phase comprises an isotactic polypropylenewith a melt flow rate of 35 g/10 minutes.

According to another aspect of the present invention, the lower-meltingdominant continuous phase is blended with a higher-melting noncontinuousphase of propylene co- and/or ter- polymers. When propylene co- and/orter-polymers are used as the higher-melting noncontinuous phase, thelower melting continuous phase may be comprised of one or morepolyethylenes selected from the group consisting of low densitypolyethylene, high pressure long chain branched polyethylene, linear lowdensity polyethylene, high density polyethylene and copolymers thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings which form a portion of the original disclosure of theinvention:

FIG. 1 diagrammatically illustrates one method and apparatus formanufacturing the nonwoven webs according to the invention;

FIG. 2 is a fragmentary plan view of a nonwoven web of the invention;

FIG. 3 is a diagrammatical cross-sectional view of a nonwoven fabriclaminate in accordance with the invention; and

FIG. 4 is a diagrammatical cross-sectional view of a laminate of thenonwoven fabric of FIG. 2 with a film.

DETAILED DESCRIPTION

Linear low density polyethylene (LLDPE) is produced in either a solutionor a fluid bed process. The polymerization is catalytic. Ziegler Nattiand single-site metallocene catalyst systems have been used to produceLLDPE. The resulting polymers are characterized by an essentially linearbackbone. Density is controlled by the level of comonomer incorporationinto the otherwise linear polymer backbone. Various alpha-olefins aretypically copolymerized with ethylene in producing LLDPE. Thealpha-olefins which preferably have four to eight carbon atoms, arepresent in the polymer in an amount up to about 10 percent by weight.The most typical comonomers are butene, hexene, 4-methyl-1-pentene, andoctene. The comonomer influences the density of the polymer. Densityranges for LLDPE are relatively broad, typically from 0.87-0.95 g/cc(ASTM D-792).

Linear low density polyethylene melt index is also controlled by theintroduction of a chain terminator, such as hydrogen or a hydrogendonator. The melt index for a linear low density polyethylene can rangebroadly from about 0.1 to about 150 g/10 min. For purposes of thepresent invention, the LLDPE should have a melt index of greater than10, and preferably 15 or greater for spunbonded filaments. Particularlypreferred are LLDPE polymers having a density of 0.90 to 0.945 g/cc anda melt index of greater than 25.

Examples of suitable commercially available linear low densitypolyethylene polymers include the linear low density polyethylenepolymers available from Dow Chemical Company, such as the ASPUN seriesof Fibergrade resins, Dow LLDPE 2500 (55 MI, 0.923 density), Dow LLDPEType 6808A (36 MI, 0.940 density), and the Exact series of linear lowdensity polyethylene polymers from Exxon Chemical Company, such as Exact2003 (31 MI, density 0.921).

The higher-melting polypropylene component can be an isotactic orsyndiotactic polypropylene homopolymer, or can be a copolymer orterpolymer of propylene. The melt flow rate of the polypropylene shouldbe greater than 20 g/10 min., and preferably 25 or greater. Particularlysuitable are polypropylene polymers having an MFR of 35 to 65. Examplesof commercially available polypropylene polymers which can be used inthe present invention include SOLTEX Type 3907 (35 MFR, CR grade),HIMONT Grade X10054-12-1 (65 MFR), Exxon Type 3445 (35 MFR), Exxon Type3635 (35 MFR) AMOCO Type 10-7956F (35 MFR), and Aristech CP 350 J (meltflow rate approximately 35). Examples of commercially availablecopolymers of propylene include Exxon 9355 which is a random propylenecopolymer with 3% ethylene, 35 melt flow rate; and co- and ter-polymersof propylene from the Catalloy™ series from Himont.

The lower-melting polyethylene component and the higher-meltingpolypropylene component can be present in proportions ranging from 70percent by weight polyethylene and 30 percent polypropylene to 99percent by weight polyethylene and 1 percent polypropylene. In theseproportions, the lower-melting polyethylene component is present as asubstantially continuous phase and the higher-melting polypropylene ispresent as a discontinuous phase dispersed in the polyethylene phase.

Appropriate combinations of polymers are combined and blended beforebeing melt-spun into fibers or fibrous webs. A high degree of mixing isused in order to prepare blends in which the polypropylene component ishighly dispersed in the polyethylene component. In some cases suchmixing may be achieved in the extruder as the polymers are converted tothe molten state. However, in other cases it may be preferred to use anextra mixing step. Among the commercially available mixers that can beused are the Barmag 3DD three-dimensional dynamic mixer supplied byBarmag AG of West Germany and the RAPRA CTM cavity-transfer mixersupplied by the Rubber and Plastics Research Association of GreatBritain.

The blended polymer dispersion is then either melt-spun into fibers,which may be formed into a web for instance by carding, airlaying, orwetlaying, or melt-spun directly into fibrous webs by a spunbonding ormeltblowing process. The web can then be bonded to form a strong, softbiconstituent-fiber nonwoven fabric. Webs of the blended polymerdispersion can be made according to any of the known commercialprocesses for making nonwoven fabrics, including processes that usemechanical, electrical, pneumatic, or hydrodynamic means for assemblingfibers into a web, for example carding, wetlaying, carding/hydroentangling, wetlaying/hydroentangling, and spunbonding. The webs ofthe blended polymer dispersion can then be bonded by a multiplicity ofthermal bonds to give the webs sufficient strength and abrasionresistance to be useful in, for example, diaper applications. Preferablythe bonds are thermal bonds formed by heating the fibers so that via acombination of heat and pressure they become tacky and fuse together atpoint of contact between the fibers. The thermal bonds may be formedusing any of the techniques known in the art for forming discretethermal bonds, such as calendering. Other thermal bonding techniques,such as through-air bonding and the like, may also be used.

FIG. 1 is a diagrammatical view of an apparatus, indicated generally bythe reference number 10, for producing a spunbonded nonwoven web inaccordance with the present invention. Various spunbonding techniquesexist, but all typically include the basic steps of extruding continuousfilaments, quenching the filaments, drawing or attenuating the filamentsby a high velocity fluid, and collecting the filaments on a surface toform a web. The spunbonding apparatus 10 is illustrated as a slotdrawtype spunbonding apparatus, although, as will be appreciated by theskilled artisan, other spunbonding apparatus may be used. Spunbondingapparatus 10 includes a melt spinning section including a feed hopper 12and an extruder 14 for the polymer. The extruder 14 is provided with agenerally linear die head or spinneret 16 for melt spinning streams ofsubstantially continuous filaments 18. The substantially continuousfilaments 18 are extruded from the spinneret 16 and typically arequenched by a supply of cooling air 20. The filaments are directed to anattenuation device 22, preferably in the form of an elongate slot whichincludes downwardly moving attenuation air which can be supplied fromforced air above the slot, vacuum below the slot, or eductively withinthe slot, as is known in the art. In the attenuation device 22, thefilaments become entrained in a high velocity stream of attenuation airand are thereby attenuated or drawn. The air and filaments aredischarged from the lower end of the attenuation device 22 and thefilaments are collected on a forming wire 24 as a nonwoven spunbond webW.

The web W is conveyed to a bonding station 26 to form a coherent bondednonwoven fabric. In the embodiment shown, the web is thermally bondedusing a pair of heated calender rolls 27 and 28. Thermal bonds areformed by heating the filaments so that they soften and become tacky,and fuse together contacting portions of the filaments. The operatingtemperature and the compression force of the heated rolls 27 and 28should be adjusted to a surface temperature and pressure such that thefilaments present in nonwoven web soften and bind the fibrous nonwovenweb to thereby form a coherent nonwoven fabric. The pattern of thecalender rolls may be any of those known in the art, including pointbonding patterns, helical bonding patterns, and the like. The term pointbonding is used herein to be inclusive of continuous or discontinuouspattern bonding, uniform or random point bonding, or a combinationthereof, all as are well known in the art.

Although bonding station 26 has been illustrated in FIG. 1 as heatedcalender rolls, the rolls can, in other embodiments of the invention, bereplaced by other thermal activation zones. For example, the bondingstation may be in the form of a through-air bonding oven, a microwave orother RF treatment zone. Other bonding stations, such as ultrasonicwelding stations, can also be used in the invention. In addition otherbonding techniques known in the art can be used, such as adhesivebonding.

The thermally bonded nonwoven fabric is then wound by conventional meansonto roll 29. The nonwoven fabric can be stored on roll 29 or passed toend use manufacturing processes, for example for use as a component in adisposable personal care article such as diapers and the like, medicalfabrics, wipes, and the like.

FIG. 2 illustrates a thermally bonded spunbonded nonwoven fabric Wproduced in accordance with the present invention. The nonwoven fabric Wmay be laminated into structures having a variety of desirable end-usecharacteristics. FIG. 3 is a diagrammatical cross-sectional view of anonwoven fabric laminate in accordance with one embodiment of theinvention. In this embodiment, the laminate, generally indicated at 40,is a two-ply laminate. Ply 41 comprises a web which may be a meltblownnonwoven web, a spunbonded web, or a web of staple fibers. Ply 42comprises a nonwoven web formed of a highly dispersed blend ofpolyolefin polymers, such as the nonwoven fabric W produced as describedabove.

The plies may be bonded and/or laminated in any of the ways known in theart. Lamination and/or bonding may be achieved, for example, byhydroentanglement of the fibers, spot bonding, through-air bonding andthe like. For example, when ply 41 is a fibrous web, lamination and/orbonding may be achieved by hydroentangling, spot bonding, through-airbonding and the like. In the embodiment shown in FIG. 3, plies 41 and 42are laminated together by passing through a heated patterned calender toform discrete thermal point bonds indicated at 43. It is also possibleto achieve bonding through the use of an appropriate bonding agent,i.e., an adhesive. The term spot bonding is inclusive of continuous ordiscontinuous pattern bonding, uniform or random point bonding or acombination thereof, all as are well known in the art.

The bonding may be made after assembly of the laminate so as to join allof the plies or it may be used to join only selected of the fabric pliesprior to the final assembly of the laminate. Various plies can be bondedby different bonding agents in different bonding patterns. Overall,laminate bonding can also be used in conjunction with individual layerbonding.

Laminates of a spunbond web from the highly blended polymer dispersionas described above with a web of meltblown microfibers have utility asbarrier fabrics in medical applications, protective clothingapplications, and for hygiene applications such as barrier leg cuffs. Ofparticular utility for hygiene applications are spunbond/meltblownlaminates of reduced basis weight, such as made with a 17 grams persquare meter (gsm) spunbonded web of this invention and 2-3 gsmmeltblown web. Such barrier laminates could be used, for example, asbarrier leg cuffs in diapers.

Another type of nonwoven fabric laminate may be made by combiningnonwoven web of this invention with a film, for example a film of athermoplastic polymer, such as a polyolefin, to make barrier fabricsuseful for hygiene applications such as barrier leg cuffs and diaperbacksheets. FIG. 4 illustrates one such laminate, which includes a plyor layer 42′ comprising a nonwoven web formed of a highly dispersedblend of polyolefin polymers, such as the nonwoven fabric W of FIG. 2,laminated to a polyolefin film layer 44, such as for example apolyethylene film of a thickness of 0.8 to 1 mil. Lamination and/orbonding of the nonwoven layer 42′ to the film layer 44 can be achievedby adhesive lamination using a continuous or discontinuous layer ofadhesive. This adhesive approach may yield a diaper backsheet withsuperior softness and hand. The nonwoven fabric laminate could also beproduced by thermal lamination of the nonwoven fabric of this inventionand film webs together. This approach has the advantage of eliminatingthe cost of the adhesive. It may also be desirable to utilize coextrudedfilm webs that include a sealing/bonding layer in combination with apolyolefin layer in the film web that, when combined with the nonwovenfabrics of the invention, maximize softness and good thermal bondingcharacteristics. The nonwoven fabric laminate could also be produced bydirect extrusion of the film layer 44 on ply 42′.

EXAMPLE 1

Ninety percent by weight of a linear low density polyethylene (LLDPE)with a melt flow of 27 (Dow 6811 LLDPE) and ten percent by weight of apolypropylene (PP) polymer with a melt flow approximately 35 (AristechCP 350 J) were dry blended in a rotary mixer. The dry-blended mixturewas then introduced to the feed hopper of an extruder of a spunbondnonwoven spinning system. Continuous filaments were meltspun by a slotdraw process at a filament speed of approximately 600 m/min anddeposited upon a collection surface to form a spunbond nonwoven web, andthe web was thermally bonded using a patterned roll with 12% bond area.For comparison purposes, nonwoven spunbond fabrics were produced undersimilar conditions with the same polymers, using 100% PP and 100% LLDPE.

As shown in table 1, the 100% LLDPE spunbond samples exhibited superiorsoftness (75 and 77.5) compared to the 100% polypropylene spunbondsample (30). However, the abrasion resistance of the 100% LLDPE sample,as seen from the fuzz measurement, was relatively high (12.5 and 2.4)compared to the 100% PP sample (0.3). The nonwoven fabric formed fromthe 90% LLDPE/10% PP blend had a high softness (67.5) only slightly lessthan the 100% LLDPE fabric, and had abrasion resistance (fuzz value) of1.0 mg., which is significantly better than the values seen for 100%LLDPE. The blend sample also showed improved CD tensile compared toproducts made with 100% LLDPE.

TABLE 1 Sample A B C D C = comparison I = invention C C C I Composition:% polypropylene 100  0  0  10 % polyethylene  0 100 100  90 filamentdia. (microns) 17.5 20.9 20.9 22.5 Basis weight (gsm)¹ 23.1 25.2 24.624.8 Loft @ 95 g/in² (mils)²  9.8  9.0  7.8  9.3 Fuzz (mg)³  0.3 12.5 2.4  1.0 Softness⁴  30 75 77.5 67.5 Strip Tensile (g/cm)⁵ CD 557 139157 164 MD 1626  757 639 467 Peak Elongation (%) CD 90 116 129 108 MD 93142 106 119 TEA (in. g./in CD 852 297 346 354 MD 2772  2222  1555  1389 ¹gsm = grams per square meter ²Loft was determined by measuring thedistance between the top and the bottom surface of the fabric sheetwhile the sheet was under compression loading of 95 grams per squareinch. The measurement is generally the average of 10 measurements. ³Fuzzis determined by repeatedly rubbing a soft elastomeric surface acrossthe face of the fabric a constant number of times. The fiber abradedfrom the fabric surface is then weighed. Fuzz is reported as mg weightobserved. ⁴Softness was evaluated by an organoleptic method wherein anexpert panel compared the surface feel of Example Fabrics with that ofcontrols. Results are reported as a softness score with higher valuesdenoting a more pleasing hand. Each reported value is from a singlefabric test sample, but reflects the input of several panel members.⁵Tensile, Peak Elongation and TEA were evaluated by breaking a one inchby seven inch long sample generally following ASTM D1682-64, theone-inch cut strip test. The instrument cross-head speed was set at 5inches per minute and the gauge length was set at 5 inches per minute.The Strip Tensile Strength, reported as grams per centimeter, isgenerally the average of at least 8 measurements. Peak Elongation is thepercent increase in length noted at maximum tensile strength. #TEA,Total Tensile Energy Absorption, is calculated from the area under thestress-strain curve generated during the Strip Tensile test.

EXAMPLE 2

(Control)

A control fiber was made by introducing 100% Dow LLDPE 2500 (55 MI,0.923 density) to a feed hopper of a spinning system equipped with anextruder, a gear pump to control polymer flow at 0.75 gram per minuteper hole, and a spinneret with 34 holes of L/D=4:1 and a diameter of 0.2mm. Spinning was carried out using a melt temperature in the extruder of215° C. and a pack melt temperature of 232° C. After air quench, theresulting filaments were drawn down at a filament speed of approximately1985 m/min using an air aspiration gun operating at 100 psig to yield adenier of 3.01 and denier standard deviation of 0.41.

EXAMPLE 3

Ninety parts by weight of Dow LLDPE Type 2500 (55 MI, 0.923 density) andten parts of Himont X10054-12-1 polypropylene (65 MFR) were dry blendedin a rotary mixer and then introduced to the feed hopper of the spinningsystem described in Example 2. Spinning was carried out using a packmelt temperature of 211° C. After air quench, the resulting filamentswere drawn down at a filament speed of approximately 2280 M/Min using anair aspiration gun operating at 100 psig to yield a denier of 2.96 and adenier standard deviation of 1.37.

EXAMPLE 4

Ninety parts by weight of Dow LLDPE Type 2500 (55 MI, 0.923 density) andten parts of Soltex 3907 polypropylene (35 MFR, 1.74 die swell, CRgrade) were dry blended in a rotary mixer and then introduced to thefeed hopper of the spinning system described in Example 2. Spinning wascarried out using a pack melt temperature of 231° C. and an extrudermelt temperature of 216° C. After air quench, the resulting filamentswere drawn down at a filament speed of approximately 2557 M/Min using anair aspiration gun operating at 100 psig to yield a denier of 2.64 and adenier standard deviation of 0.38.

EXAMPLE 5

Ninety parts by weight of Dow LLDPE Type 6808A (36 MI, 0.940 density)and ten parts of Soltex 3907 polypropylene (35 MFR, 1.74 die swell, CRgrade) were dry blended in a rotary mixer and then introduced to thefeed hopper of the spinning system described in Example 2. Spinning wascarried out using a pack melt temperature of 231° C. and an extrudermelt temperature of 216° C. After air quench, the resulting filamentswere drawn down at a filament speed of approximately 2129 M/Min using anair aspiration gun operating at 100 psig to yield a denier of 3.17 and adenier standard deviation of 2.22.

The quality of spinning for a given formulation has been found toroughly correlate with the denier standard deviation. A reduced standarddeviation suggests more stable or higher quality spinning. Thus it isunexpected and contrary to the teaching of the prior art that the blendusing a 35 MFR polypropylene in Example 4 yielded a more stable spinningthan seen with the corresponding LLDPE control in Example 2.

EXAMPLE 6

Eighty parts by weight of a linear low density polyethylene pellets of55 melt index and 0.925 g/cc density and twenty parts by weightpolypropylene pellets of 35 melt flow rate were dry blended in a rotarymixer. The dry-blended mixture was then introduced to the feed hopper ofa spinning system equipped with an extruder with a 30:1 l/d ratio, astatic mixer, and a gear pump for feeding the molten polymer to a heatedmelt block fitted with a spinneret. Filaments were extruded from thespinneret and drawn using air aspiration.

EXAMPLE 7

Samples of continuous filament spunbonded nonwoven webs were producedfrom blends of a linear low density polyethylene with a melt flow rateof 27 (Dow 6811A LLDPE) and a polypropylene homopolymer (Appryl 3250YR1,27 MFR) in various blend proportions. Control fabrics of 100 percentpolypropylene and 100 percent polyethylene were also produced undersimilar conditions. The fabrics were produced by melt spinningcontinuous filaments of the various polymers or polymer blends,attenuating the filaments pneumatically by a slot draw process,depositing the filaments on a collection surface to form webs, andthermally bonding the webs using a patterned calender roll with a 12percent bond area. The fabrics had a basis weight of approximately 25gsm and the filaments had an average mass/length of 3 dtex. The tensilestrength and elongation properties of these fabrics and their abrasionresistance were measured, and these properties are listed in Table 2. Asshown, the 100 percent polypropylene control fabric had excellentabrasion resistance, as indicated by no measurable fuzz generation;however the fabrics had relatively low elongation. The 100 percentpolyethylene control fabric exhibited good elongation properties, butvery poor abrasion resistance (high fuzz values and low Taber abrasionresistance) and relatively low tensile strength. Surprisingly, thefabrics of the invention made of blends of polypropylene andpolyethylene exhibited an excellent combination of abrasion resistance,high elongation, and good tensile strength. It is noted that the CDelongation values of the blends actually exceeded that of the 100%polyethylene control. This surprising increase in elongation is believedto be attributable to the better bonding of the filaments of the blendas compared to the bonding achieved in the 100% polyethylene control,which resulted in the fabrics of the invention making good use of thehighly elongatable filaments without bond failure.

TABLE 2 MECHANICAL PROPERTIES OF POLYPROPYLENE (PP)/POLYETHYLENE (PE)BLEND FABRICS 25/75 15/85 Fabric 100% PP PP/PE PP/PE 100% PE MD Tensile(g/cm)⁶ 925 764 676 296 CD Tensile (g/cm)⁶ 405 273 277  63 MD Elongation(%)⁶  62 170 199 168 CD Elongation (%)⁶  70 190 224 131 Fuzz (mg)⁷ 0.00.3 0.5 19.0 Taber Abrasion⁸  40  32  22  10 (cycles - rubber wheel)Taber Abrasion⁸ 733 200 500  15 (cycles - felt wheel) ⁶Tensile and PeakElongation were evaluated by breaking a one inch by seven inch longsample generally following ASTM D1682-64, the one-inch cut strip test.The instrument cross-head speed was set at 5 inches per minute and thegauge length was set at 5 inches per minute. The Strip Tensile Strength,reported as grams per inch, is generally the average of at least 8measurements. Peak Elongation is the percent increase in length noted atmaximum tensile strength. ⁷Fuzz is determined by repeatedly rubbing asoft elastomeric surface across the face of the fabric a constant numberof times. The fiber abraded from the surface is then weighed. Fuzz isreported as mg weight observed. ⁸Conducted according to ASTM D3884-80where the number of cycles was counted until failure. Failure wasdefined as the appearance of a hole of one square millimeter or greaterin the surface of the fabric.

That which we claim is:
 1. A nonwoven fabric laminate comprising anonwoven fabric comprised of fibrous material in the form of continuousfilaments or staple fibers of a size less than 15 dtex/filament randomlyarranged and bonded to one another at discrete locations, said fibrousmaterial being formed of a dispersed blend of at least two differentpolyolefin polymers, said polymers being present as a lower-meltingdominant continuous phase and at least one higher-melting noncontinuousphase dispersed therein, said lower-melting continuous phase forming atleast 70 percent by weight of said fibrous material and comprising alinear low density polyethylene polymer of a melt index of greater than10 g/10 min. and a density of less than or about 0.945 g/cc and said atleast one higher-melting noncontinuous phase comprising a polypropylenepolymer with melt flow rate of greater than 20 g/10 min.; and at leastone other web bonded to said nonwoven fabric to form a unitary nonwovenlaminate structure, wherein a ratio of said melt index of said linearlow density polyethylene polymer to said melt flow rate of saidpolypropylene polymer ranges from about 0.5 to about 1.57.
 2. A nonwovenfabric laminate according to claim 1, wherein said nonwoven fabric isbonded to said at least one other web by hydroentanglement, thermalbonding or adhesive bonding.
 3. A nonwoven fabric laminate according toclaim 1, including a multiplicity of discrete thermal bonds bonding saidnonwoven fabric to said at least one other web.
 4. A nonwoven fabriclaminate according to claim 1, wherein said at least one other webcomprises a web of meltblown microfibers.
 5. A nonwoven fabric laminateaccording to claim 1, wherein said at least one other web comprises apolymer film.
 6. A nonwoven fabric laminate according to claim 1,wherein said polypropylene polymer comprises a copolymer ofpolypropylene with up to 5 percent by weight ethylene.
 7. A nonwovenfabric laminate according to claim 1, wherein said lower-meltingcontinuous phase forms at least 80 percent by weight of the fiber andcomprises a linear low density polyethylene having a density of0.90-0.945 g/cc and a melt index of greater than 25 g/10 min.
 8. Anonwoven fabric laminate according to claim 1, wherein saidlower-melting polymer phase comprises at least 80 percent by weightlinear short chain branched polyethylene with a melt index of greaterthan 50 g/10 min. and a density of 0.925 g/cc and said higher-meltingpolymer phase comprises 1 to 20 percent by weight of an isotacticpolypropylene with a melt flow rate greater than 20 g/10 minutes.
 9. Anonwoven fabric laminate according to claim 1, wherein saidlower-melting polymer phase comprises linear low density polyethylenewith a melt index of 27 g/10 min. and said higher-melting polymer phasecomprises an isotactic polypropylene with a melt flow rate of 35 g/10minutes.
 10. A nonwoven fabric alminate according to claim 1, whereinsaid nonwoven fabric includes a multiplicity of thermal bonds.
 11. Anonwoven fabric laminate according to claim 1, wherein said fiberscomprises continuous filamentary strands randomly disposed and bonded toone another to form a spunbonded fabric.
 12. A nonwoven fabric laminatecomprising a spunbonded nonwoven web comprised of continuous filamentsof a size less than 15 dtex/filament randomly arranged and bonded to oneanother at discrete locations, said continuous filaments being formed ofa dispersed blend of at least two different polyolefin polymers, saidpolymers being present as a lower-melting dominant continuous phase andat least one higher-melting noncontinuous phase dispersed therein, saidlower-melting continuous phase forming at least 70 percent by weight ofthe filaments and comprising a linear low density polyethylene polymerof a melt index of greater than 10 g/10 min. and a density of less thanor about the 0.945 tl g/cc and said at lest one higher-meltingnoncontinuous phase comprising a polypropylene polymer with melt flowrate of greater than 20 g/10 min.; and at least one other web bonded tosaid spunbonded nonwoven web to form a unitary nonwoven laminatestructure, wherein a ratio of said melt index of said linear low densitypolyethylene polymer to said melt flow rate of said polypropylenepolymer ranges from about 0.5 to about 1.57.
 13. A nonwoven fabriclaminate comprising a nonwoven web of staple fibers of a size less than15 dtex/filament randomly arranged and bonded to one another at discretelocations, said fibers being formed of a dispersed blend of at least twodifferent polyolefin polymers, said polymers being present as alower-melting dominant continuous phase and at least one higher-meltingnoncontinuous phase dispersed therein, said lower-melting continuousphase forming at least 70 percent by weight of the fiber and comprisinga linear low density polyethylene polymer of a melt index of greaterthan 10 g/10 min. and a density of less than or about 0.945 g/cc andsaid at least one higher-melting noncontinuous phase comprising apolypropylene polymer with melt flow rate of greater than 20 g/10 min.;and at least one other web bonded to said nonwoven web to form a unitarynonwoven laminate structure, wherein a ratio of said melt index of saidlinear low density polyethylene polymer to said melt flow rate of saidpolypropylene polymer ranges from about 0.5 to about 1.57.
 14. Anonwoven fabric laminate comprising a nonwoven fabric comprised offibrous material in the form of continuous filaments of a size less than15 dtex/filament randomly arranged and bonded to one another at discretelocations, said fibrous material being formed of a dispersed blend of atleast two different polyolefin polymers, said polymers being present asa lower-melting dominant continuous phase and at least onehigher-melting noncontinuous phase dispersed therein, said lower-meltingcontinuous phase forming at least 70 percent by weight of said fibrousmaterial and comprising a linear low density polyethylene polymer of amelt index of a melt index of greater than 10 g/10 min. and a density ofless than or about 0.945 g/cc and said at least one higher-meltingnoncontinuous phase comprising isotactic polypropylene with a melt flowrate of greater than 20 g/10 min.; and at least one meltblown webthermally bonded to said nonwoven fabric to form a unitary nonwovenlaminate structure, wherein a ration of said melt index melt index ofsaid linear low density polyethylene polymer to said melt flow rate ofsaid polyproylene polymer ranges from about 0.5 to about 1.57.
 15. Anonwoven fabric laminate according to claim 1, wherein a ratio of saidmelt index of said linear low density polyethylene polymer to said meltflow rate of said polypropylene polymer ranges from about 0.77 to about1.57.
 16. The nonwoven fabric laminate according to claim 12, wherein aratio of said melt index of said linear low density polyethylene polymerto said melt flow rate of said polypropylene polymer ranges from about0.77 to about 1.57.
 17. The nonwoven fabric laminate according to claim13, wherein a ratio of said melt index of said linear low densitypolyethylene polymer to said melt flow rate of said polypropylenepolymer ranges from about 0.77 to about 1.57.
 18. The nonwoven fabriclaminate according to claim 17, wherein a ratio of said melt index ofsaid linear low density polyethylene polymer to said melt flow rate ofsaid polypropylene polymer ranges from about 0.77 to about 1.57.